Organic electroluminescent device

ABSTRACT

The present invention discloses an “organic light-emitting device (OLED)”, comprising an anode, a cathode, and one or more organic layers, wherein the said organic layer contains at least one compound having the formula (I), and the said OLED has the advantages of excellent light-emitting efficiency, excellent color purity and long lifetime.

TECHNICAL FIELD

This invention relates to a new type of organic blue light-emitting OLEDproduced by organic electronic material, which belongs to OLED displaytechnology field.

BACKGROUND ART

OLED, as a new type of display technology, has unique advantages such asself-illumination, wide viewing angle, low power consumption, highefficiency, thin, rich colors, fast response, extensive applicationtemperature range, low driving voltage, applicable for flexible andtransparent display panel, and environmental friendliness, etc.Therefore, OLED technology can be applied to flat panel displays and newgeneration of lighting, or can be used as backlight of LCD.

OLED is a device made through spin-coating or depositing organicmaterial layers between two electrodes. A classic three-layer OLEDcomprises a hole transport layer, a light emitting layer and an electrontransport layer. The holes injected from the anode and hopping throughthe hole transport layer, and the electrons injected from the cathodeand hopping through the electron transport layer combine to formexcitons in the light emitting layer and emit light. By changing thematerials of the light emitting layer, the OLED can emit red, green andblue light. Therefore, stable, efficient organic light-emittingmaterials with pure colors play an important role in the application andpromotion of OLEDs, and are urgently needed for the application andpromotion of large area panel display in OLEDs.

Among three primary colors (red, blue, green), the red and greenemitting materials have made great development, which also meet themarket demands of the panels. There are a series of commerciallyavailable materials for the blue light emission, such as4,4′-bis(2,2′-diphenyl vinyl)-1,1′-biphenyl (DPVBi) compounds producedby Idemitsu are widely used in the early period. The devices made bythis type of compounds have high efficiency, but these materials oftenhave poor stability, and even worse, this type of compounds often emitsky-blue light, with CIE_(y)>0.15. Therefore, its poor stability andimpure color greatly restrict the application of this type of compoundsin the full-color display devices. Some other blue-light materials, suchas ADN and tetra-butyl perylene made by Kodak, have relatively poorluminous efficiency and cannot be widely used.

SUMMARY OF THE INVENTION

In the present invention, a kind of blue light-emitting OLED with goodelectroluminescent efficiency, excellent color purity and long lifetimeis provided to overcome the deficiencies of the above devices.

An organic light-emitting device comprises an anode, a cathode, and oneor more organic layers, wherein the said organic layer contains at leastone compound having the formula I:

Wherein, R₁-R₈ independently represent hydrogen, deuterium, halogen,cyano, nitro, C1-C8 alkyl, C1-C8 alkoxy, C6-C30 substituted orunsubstituted aryl, C3-C30 substituted or unsubstituted heteroarylcontaining one or more heteroatoms, C2-C8 substituted or unsubstitutedalkenyl, C2-C8 substituted or unsubstituted alkynyl, wherein, Ar₁-Ar₄represent independently C6-C60 substituted or unsubstituted aryl, C3-C60substituted or unsubstituted heteroaryl containing one or moreheteroatoms, triaryl (C6-C30) amine.

Preferably, wherein R₁-R₈ independently represent hydrogen, halogen,cyano, nitro, C1-C8 alkyl, C1-C8 alkoxy, C2-C8 substituted orunsubstituted alkenyl, C2-C8 substituted or unsubstituted alkynyl, C1-C4alkyl substituted or unsubstituted phenyl, C1-C4 alkyl substituted orunsubstituted naphthyl; Ar₁-Ar₄ independently represent C1-C4 alkyl orC6-C30 aryl substituted phenyl, C1-C4 alkyl or C6-C30 aryl substitutednaphthyl, phenyl, naphthyl, N-aryl (C6-C30) or C1-C4 alkyl-substitutedcarbazolyl, dibenzothiophenyl, dibenzofuranyl, anthryl, phenanthryl,pyrenyl, perylenyl, fluoranthenyl, (9,9-di-alkyl) fluorenyl,(9,9-dialkyl-substituted or unsubstituted aryl) fluorenyl,9,9-spiro-fluorenyl.

Preferably, wherein R₁-R₈ independently represent hydrogen, halogen,C1-C4 alkyl, C1-C4 alkyl substituted or unsubstituted phenyl, C1-C4alkyl substituted or unsubstituted naphthyl; preferably, Ar₁-Ar₄independently represent phenyl, tolyl, t-butyl phenyl, naphthyl, methylnaphthalene, biphenyl, diphenyl phenyl, naphthyl phenyl,diphenyl-biphenyl, biaryl amine pheny, N-phenyl-carbazolyl,(9,9-di-alkyl) fluorenyl, (9,9-dialkyl-substituted or unsubstitutedphenyl) fluorenyl, 9,9-spiro-fluorenyl.

Preferably, wherein, R₁, R₄, R₅, R₈ are hydrogen, R₂, R₃, R₆, R₇independently represent hydrogen, fluorine, methyl, ethyl, propyl,isopropyl, tert-butyl, phenyl, naphthyl; Ar₁-Ar₄ independently representphenyl, tolyl, naphthyl, methyl naphthyl, biphenyl, diphenyl phenyl,naphthyl phenyl, diphenyl-biphenyl, (9,9-di-alkyl) fluorenyl,(9,9-dimethyl-substituted or unsubstituted phenyl) fluorenyl,9,9-spiro-fluorenyl.

Preferably, wherein Ar₂, Ar₃, Ar₄ independently represent phenyl,naphthyl, biphenyl, Ar₁ is phenyl, naphthyl, biphenyl, diphenyl phenyl,naphthyl phenyl, diphenyl-biphenyl, (9,9-di-alkyl) fluorenyl, (9-tolyl,9′-phenyl) fluorenyl, 9,9-spiro-fluorenyl.

Preferably, wherein R₂, R₃, R₆, R₇ are hydrogen, Ar₂, Ar₃, Ar₄independently represent phenyl, naphthyl.

Preferably, the said compound with formula (I) is the compound with thefollowing structures:

The said organic layers is one or more layers that may contain holeinjection layer, hole transport layer, light emitting layer, holeblocking layer and electron transport layer. It should be particularlynoted that, not all organic layers are necessary according to the needs.

The said hole transport layer, electron transport layer and/or lightemitting layer may contain the compound with formula (I).

The said compound with formula (I) is located at the light emittinglayer.

The OLED in the present invention comprises a light-emitting layer, andthe emission wavelength is within the range of 380-740 nm, covering theentire white zone. Preferably, the emission is within the range of380-550 nm, and more preferably in the blue region within the range of440-490 nm.

The said light-emitting layer is a non-doped system or guest-host dopedsystem composed of host material and guest material.

The said compound with formula (I) is host material and/or guestmaterial.

In the doped system, the concentration of host material is 20-99.9% ofthe whole light emitting layer in weight, preferably 80-99%, morepreferably 90-99%; while the concentration of guest material is 0.01-80%of the whole light emitting layer in weight, preferably 1-20%, morepreferably 1-10%.

The total thickness of the organic layers of electronic device in thepresent invention is 1-1000 nm, preferably 1-500 nm, more preferably50-300 nm.

The said organic layer can be formed as thin film by vacuum evaporatingor spin coating.

As mentioned above, the said compound with formula (I) in the presentinvention is exemplified as follows, but not limited to the structuresas below:

The materials of the hole transport layer and hole injection layer inthe present invention should have good hole transport performance, whichcan effectively transport the holes from the anode to the organic lightemitting layer. The materials used can include small molecule or polymerorganic materials, including but not limited to triaryl amine compounds,benzidine compounds, thiazole compounds, oxazole compounds, imidazolecompounds, fluorene compound, phthalocyanine compounds,dipyrazino[2,3-f:2′,3-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile(HAT-CN), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane(F4-TCNQ), polyvinyl carbazole, polythiophene, polyethylene, polystyrenesulfonic acid.

The organic light emitting layer in the present invention can contain,in addition to the invented anthracene vinyl compounds, the followingbut not limited to the following compounds: naphthalene compounds,pyrene compounds, fluorene compounds, phenanthrene compounds, chrysenecompounds, fluoranthene compounds, anthracene compounds, pentacenecompounds, perylene compound, bi-aryl vinyl compounds, triphenylaminevinyl compounds, amine compounds, benzimidazole compounds, furancompounds and organic metal chelate compounds.

The organic electron transport material of the organic electronicdevices in the present invention should have good electron-transportperformance, which can efficiently transport electrons from the cathodeto the light emitting layer. These materials can be selected from thefollowing compounds, but not limited to oxazole, thiazoles compounds,triazole compounds, triazine compounds, tri-aza benzene compounds,quinoxaline compounds, di-aza anthracene compounds, silicon-containingheterocyclic compounds, quinoline compounds, phenanthroline compounds,metal chelates, fluoro-substituted benzene compounds.

One electron injection layer can be added to the organic electronicdevice of the present invention as required. The electron injectionlayer can effectively inject electrons from the cathode into the organiclayer, and could be mainly selected from alkali metals or alkali metalcompounds, or selected from alkaline earth metals or alkaline earthmetal compounds, including but not limited to the following: lithium,lithium fluoride, lithium oxide, lithium nitride, 8-hydroxyquinolatolithium, cesium, cesium carbonate, 8-hydroxyquinolato cesium, calcium,calcium fluoride, calcium oxide, magnesium, magnesium fluoride,magnesium carbonate, magnesium oxide.

Experimental results show that, the OLEDs in the present invention haveadvantages of good light-emitting efficiency, excellent color purity andlong lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural drawing of the device,

of which, 10 denotes a glass substrate, 20 denotes an anode, 30 denotesa hole injection layer, 40 denotes a hole transport layer, 50 denotes alight emitting layer, 60 denotes an electron transport layer, 70 denotesan electron injection layer, 80 denotes a cathode.

FIG. 2 is the ¹H NMR spectrum of compound 110.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

In the following, the present invention is described in details bygiving the following examples.

Embodiment 1 Synthesis of Compound 110

Synthesis of Intermediate 1-1

To a 1 L single-necked flask, was added 25.5 g 1-naphthaleneboronic acidand 25 g bromobenzaldehyde, 400 ml dioxane, 80 ml 2 M potassiumcarbonate solution, 1.0 g tetrakis(triphenylphosphine)palladium underthe protection of nitrogen. The mixture was refluxed for 12 hours,cooled down, and extracted three times with ethyl acetate. The organicphase was dried over anhydrous sodium sulfate, concentrated, andrecrystallized from ethanol to yield 29 g solid (92%).

Synthesis of Intermediate 1-3

To a 500 ml single-neck flask, was added 25 g p-bromobenzyl bromide and49.8 ml triethyl phosphite (1-2). The mixture was refluxed for 2 hours,then the excess triethyl phosphate was removed. 23.4 g intermediate 1-1,250 ml DMF, and 16.8 g potassium tert-butoxide were added into the flaskin an ice bath. The resulting mixture was allowed to warm to the roomtemperature, and stirred overnight. The reaction mixture was poured intodistilled water, filtered, and the precipitate was recrystallized fromethanol to yield 31.8 g product (83%).

Synthesis of Intermediate 1-4

To a 1 L one-neck flask, was added 45 g 3,5-diphenylphenyl boronic acidand 42.5 g 1-bromo-4-iodobenzene, 450 ml dioxane, 150 ml 2M potassiumcarbonate aqueous solution, and 1.7 gtetrakis(triphenylphosphine)palladium under nitrogen. The mixture wasrefluxed for 12 hours, cooled down, and extracted three times with ethylacetate. The organic phase was dried over anhydrous sodium sulfate,concentrated, and the crude product was recrystallized from ethanol toyield 54.6 g product (95%).

Synthesis of Intermediate 1-5

With the protection of nitrogen, 20 g intermediate 1-4 and 300 ml THFwere added into a 1 L three-necked flask. To the above solution wasadded dropwise 21 ml 2.5M n-butyl lithium under −78° C. and kept for 2hours. Then 16.6 g triisopropyl borate was added and kept for anotherhour. The mixture was allowed to warm to room temperature and reactedfor another 12 hours. The reaction mixture was neutralized with 2Ndilute hydrochloric acid, and extracted three times with ethyl acetate.The resulting organic phase was dried over anhydrous sodium sulfate,concentrated, and the crude product was recrystallized from ethylacetate and n-hexane to yield 14 g product (78%).

Synthesis of Intermediate 1-6

To a 500 ml single-neck flask, was added 20 g intermediate 1-3, 14 g9-anthraceneboronic acid, 350 ml dioxane, 70 ml potassium carbonatesolution, and 0.6 g tetrakis(triphenylphosphine)palladium undernitrogen. The mixture was refluxed for 12 hours, cooled down, andextracted three times with ethyl acetate. The organic phase was driedover anhydrous sodium sulfate, and concentrated. The crude product wasstirred in boiling THF, cooled down, filtered, and dried to yield 20 gproduct (80%).

Synthesis of Intermediate 1-7

To a 500 ml single-neck flask, was added 20 g intermediate 1-6, 10.4 gNBS and 400 ml chloroform. The mixture was stirred at 25° for 12 hours,then concentrated, and recrystallized from THF and ethanol to give 17 gproduct (73.3%).

Synthesis of Compound 110

To a 250 ml single-neck flask, was added 5.5 g intermediate 1-5, 7.3 gintermediate 1-7, 75 ml dioxane, 20 ml 2M potassium carbonate aqueoussolution, 0.15 g tetrakis(triphenylphosphine)palladium under nitrogen.The mixture was refluxed for 12 hours, cooled down, and extracted threetimes with ethyl acetate. The organic phase was dried over anhydroussodium sulfate, and concentrated. The crude product was stirred inboiling THF, cooled down, filtered, and dried to give 7.7 g product(75.5%). ¹H NMR (400 MHz, CD₂Cl₂), δ: 7.99-8.02 (m, 5H), 7.88-7.95 (m,3H), 7.76-7.86 (m, 12H), 7.38-7.63 (m, 22H); MALDI-TOF-MS m/z found786.5, C₆₂H₄₂ [M⁺] requires 786.3. The ¹H NMR of compound 110 is shownin FIG. 2.

Embodiment 2 Synthesis of compound 122

Synthesis of Intermediate 2-2

With the protection of nitrogen, 36.3 g intermediate (2-1) and 400 mlTHF were added into a 1 L three-necked flask, which was cooled down to−78° C. followed by adding dropwise 50 ml 2.5M n-butyl lithium and keptstirring for 2 hours. Then 30 g triisopropyl borate was added and themixture was kept stirring at low temperature for another 1 hour beforeallowed to warm to room temperature and stirred for another 12 hours. 2Ndilute hydrochloric acid was added to neutralize the reaction mixture,which was then extracted three times with ethyl acetate. The organicphase was dried over anhydrous sodium sulfate, concentrated, andrecrystallized from ethyl acetate and n-hexane to yield 27 g product(90%).

Synthesis of Intermediate 2-3

To a 500 ml one-neck flask, was added 25 g intermediate 2-2, 14.5 g1-bromo-4-iodobenzene, 300 ml dioxane, 60 ml 2M potassium carbonateaqueous solution, 0.6 g tetrakis(triphenylphosphine)palladium undernitrogen. The mixture was refluxed for 12 hours, cooled down, andextracted three times with ethyl acetate. The organic phase was driedover anhydrous sodium sulfate, and concentrated. The crude product waswashed in refluxing THF, cooled down, filtered, and dried to yield 22 gproduct (70%).

Synthesis of Intermediate 2-4

With the protection of nitrogen gas, 15.5 g intermediate 2-3 and 300 mlTHF was added into a 250 ml three-necked flask, which was cooled down to−78° C. followed by adding dropwise 17 ml 2.5M n-butyl lithium and keptstirring for 2 hours. Then 10.2 g triisopropyl borate was added and themixture was kept stirring at low temperature for another 1 hour beforeallowed to warm to room temperature and stirred for another 12 hours. 2Ndilute hydrochloric acid was added to neutralize the reaction mixture,which was then extracted three times with ethyl acetate. The organicphase was dried over anhydrous sodium sulfate, concentrated, and thecrude product recrystallized from ethyl acetate and n-hexane to yield 14g product (90%).

Synthesis of Compound 122

To a 250 ml single-neck flask was added 7 g intermediate 2-5, 8 gintermediate 1-7, 120 ml dioxane, 24 ml 2M potassium carbonate aqueoussolution, 0.16 g tetrakis(triphenylphosphine)palladium under nitrogen.The mixture was refluxed for 12 hours, cooled down, and extracted threetimes with ethyl acetate. The organic phase was dried over anhydroussodium sulfate and concentrated. The crude product was washed inrefluxing THF, cooled down, filtered and dried to yield 10 g product(79%). ¹H NMR (400 MHz, CD₂Cl₂,) δ: 7.98-8.00 (d, J=8.4 Hz, 2H),7.94-7.96 (d, J=7.6 Hz, 2H), 7.89-7.91 (d, J=8.0 Hz, 2H), 7.76-7.86 (m,12H), 7.65-7.67 (d, J=8.4 Hz, 2H), 7.48-7.58 (m, 11H), 7.32-7.43 (m,11H), 7.09-7.17 (m, 6H) 2.32 (s, 3H). The calculated value ofMALDI-TOF-MS m/s C₇₀H₄₈: 888.4; measured value [M⁺]: 888.7.

Embodiment 3

An illustrative preparation process of blue OLED adopting the organicelectronic material in the present invention is given as below.

Firstly, the transparent glass substrate 10 (with conductive ITO asanode 20 above) was washed with detergent solution, deionized water,ethanol, acetone, deionized water in sequence, then treated with oxygenplasma for 30 seconds, and then treated with CF_(x) plasma.

-   -   A 5 nm-thick film of MoO₃ was evaporated on top of ITO, which is        used as the hole injection layer 30.    -   A 50 nm-thick film of P1 was evaporated as the hole transport        layer 40.    -   A 20 nm-thick film of compound 110 was evaporated above the hole        transport layer as the light emitting layer 50.    -   A 40 nm-thick film of P2 was evaporated above the light emitting        layer as the electron transport layer 60.    -   Finally, a 1.2 nm-thick LiF film was evaporated as the electron        injection layer 70, and a 150 nm-thick Al film was evaporated as        the device cathode 80.

The device could achieve blue emission with luminance of 980 cd/m²,current efficiency of 4.3 cd/A, power efficiency of 2.1 lm/W at adriving voltage of 7 V.

The said structural formula of the chemicals used in the device

Embodiment 4 (the Device Fabrication Procedures were the Same as that inEmbodiment 3)

OLED was made using compound 122 instead of compound 110.

The device could achieve blue emission with luminance of 470 cd/m²,current efficiency of 4.6 cd/A, and power efficiency of 1.95 lm/W at adriving voltage of 7 V.

Comparison Example 1

The device fabrication procedures were the same as that in Embodiment 3.OLED was made using the following compound P3 instead of compound 110for comparison.

The device could achieve blue emission with luminance of 289 cd/m²,current efficiency of 2.4 cd/A, and power efficiency of 1.1 lm/W at adriving voltage of 7 V.

The embodiments 3 and 4 are two specific applications of the material inthe present invention. The OLED devices using the invented material canachieve blue emission with higher brightness and efficiency that in thecomparison example. Therefore, the stable material in the presentinvention is proved to give high efficiency and high color purity inelectroluminescent devices.

What is claimed is:
 1. An organic light-emitting device (OLED) comprisesan anode, a cathode, and one or more organic layers, wherein the saidone or more organic layers contains at least one compound having theformula I:

wherein, R₁-R₈ independently represent hydrogen, halogen, cyano, nitro,C1-C8 alkyl, C1-C8 alkoxy, C2-C8 substituted or unsubstituted alkenyl,C2-C8 substituted or unsubstituted alkynyl, C1-C4 alkyl substituted orunsubstituted phenyl, or C1-C4 alkyl substituted or unsubstitutednaphthyl; and, Ar₁-Ar₄ independently represent C1-C4 alkyl or C6-C30aryl substituted phenyl, C1-C4 alkyl or C6-C30 aryl substitutednaphthyl, phenyl, naphthyl, C6-C30 N-aryl or C1-C4 alkyl-substitutedcarbazolyl, dibenzothiophenyl, dibenzofuranyl, anthryl, phenanthryl,pyrenyl, perylenyl, fluoranthenyl, (9,9-di-alkyl) fluorenyl,(9,9-dialkyl-substituted or unsubstituted aryl) fluorenyl, or9,9-spiro-fluorenyl.
 2. The OLED according to claim 1, wherein: R₁-R₈independently represent hydrogen, halogen, C1-C4 alkyl, C1-C4 alkylsubstituted or unsubstituted phenyl, or C1-C4 alkyl substituted orunsubstituted naphthyl; and Ar₁-Ar₄ independently represent phenyl,tolyl, t-butyl phenyl, naphthyl, methyl naphthalene, biphenyl, diphenylphenyl, naphthyl phenyl, diphenyl-biphenyl, biaryl amine phenyl,N-phenyl-carbazolyl, (9,9-di-alkyl) fluorenyl, (9,9-dialkyl-substitutedor unsubstituted phenyl) fluorenyl, or 9,9-spiro-fluorenyl.
 3. The OLEDaccording to claim 2, wherein, R₁, R₄, R₅, and R₈ are hydrogen, R₂, R₃,R₆, and R₇ independently represent hydrogen, fluorine, methyl, ethyl,propyl, isopropyl, tert-butyl, phenyl, or naphthyl; and Ar₁-Ar₄independently represent phenyl, tolyl, naphthyl, methyl naphthyl,biphenyl, diphenyl phenyl, naphthyl phenyl, diphenyl-biphenyl,(9,9-di-alkyl) fluorenyl, (9,9-dimethyl-substituted or unsubstitutedphenyl) fluorenyl, or 9,9-spiro-fluorenyl.
 4. The OLED according toclaim 3, wherein: Ar₂, Ar₃, and Ar₄ independently represent phenyl,naphthyl, or biphenyl, and Ar₁ is phenyl, naphthyl, biphenyl, diphenylphenyl, naphthyl phenyl, diphenyl-biphenyl, (9,9-di-alkyl) fluorenyl,(9-tolyl, 9′-phenyl) fluorenyl, or 9,9-spiro-fluorenyl.
 5. The OLEDaccording to claim 4, wherein: R₂, R₃, R₆, and R₇ are hydrogen, and Ar₂,Ar₃, and Ar₄ independently represent phenyl or naphthyl.
 6. An organiclight-emitting device (OLED) comprises an anode, a cathode, and one ormore organic layers, wherein the said one or more organic layerscontains at least one compound having one of the following structures:


7. The OLED according to claim 6, wherein the said at least one compoundis one or more of the following compounds:


8. The OLED according to claim 1, wherein the said one or more organiclayers is one or more layers that may contain one or more of: holeinjection layer, hole transport layer, light emitting layer, holeblocking layer, or electron transport layer.
 9. The OLED according toclaim 8, wherein the said hole transport layer, electron transport layerand/or light emitting layer contains the said at least one compound withformula (I).
 10. The OLED according to claim 9, wherein the said atleast one compound with formula (I) is located at the light emittinglayer.
 11. The OLED according to claim 10, wherein the saidlight-emitting layer is a non-doped system or guest-host doped systemcomposed of a host material and/or guest material.
 12. The OLEDaccording to claim 11, wherein the said at least one compound withformula (I) is the host material and/or guest material.